Apparatus for preparing a coffee extract with a fine-bubble froth layer using a liquid flow decelerating barrier

ABSTRACT

The invention relates to an apparatus for preparing a coffee extract with a fine-bubble froth layer, provided with at least one inlet ( 2 ) to which coffee extract is supplied, at least one outlet ( 4.1; 4.2 ) for dispensing the coffee extract with the fine-bubble froth layer and at least one liquid flow path ( 6 ) extending from the at least one inlet to the at least one outlet ( 2 ) and along which, in use, the coffee extract flows from the at least one inlet to the at least one outlet ( 4.1; 4.2 ), while in the at least one liquid flow path a buffer reservoir is included with an upright sidewall and a bottom, the at least one inlet being provided with at least one spout opening for generating at least one coffee extract is supplied to the at least one inlet. According to the invention, in the buffer reservoir, a liquid flow decelerating barrier located at a distance from the upright sidewalls is included.

This invention relates to an apparatus for preparing a coffee extractwith a fine-bubble froth layer, provided with at least one inlet towhich coffee extract is supplied, at least one outlet for dispensing thecoffee extract with fine-bubble froth layer and at least one liquid flowpath extending from the at least one inlet to the at least one outletand along which, in use, the coffee extract flows from the at least oneinlet to the at least one outlet, while in the liquid flow path a bufferreservoir is included with an upright sidewall and a bottom, the atleast one inlet being provided with at least one spout opening forgenerating at least one coffee extract jet which, in use, squirts intothe buffer reservoir when the coffee extract is supplied to the at leastone inlet.

Such an apparatus is known from European patent application No. 0 878158.

It appears that such an apparatus is especially satisfactory forpreparing a coffee extract with a fine-bubble froth layer (also calledcafé crème). The fine-bubble froth layer are coffee bubbles which arefilled with air.

Although the respective apparatus is very satisfactory, the inventionaims to improve the apparatus in the sense that the range of the flowrate of the at least one coffee extract jet, in which a uniformfine-bubble froth layer is formed, is increased. In particular, theinvention aims to provide that a same or comparable fine-bubble frothlayer is formed when the flow rate mentioned increases. Variation of theflow rate, more in particular increase of the flow rate, can be a resultof, for instance, ageing of the apparatus. Often, the apparatus isprovided with means known per se for supplying coffee extract, underpressure, to the inlet. These means, known per se, such as a“Napolitane” apparatus, or an apparatus comprising a pump for generatingpressure, have as a property that the pressure of the coffee extract canvary. This variation can be related to the age of the apparatus.However, this variation is even more strongly related to the thicknessof the coffeebed through which hot water has to be pressed for obtainingthe coffee extract which is supplied to the at least one inlet. With anincrease of the thickness, the pressure drop across the coffeebed willincrease, resulting in a decrease of the pressure of the coffee extractbeing supplied to the inlet. Conversely, the pressure of the coffeeextract which is supplied to the inlet will increase when the thicknessof the coffee bed decreases. As a result, the flow rate of at least onecoffee extract jet will increase. Also, when the grain size of theground core of the coffee bed increases, the pressure will increase. Asa result, the flow rate of the at least one coffee extract jet willincrease. It is, therefore, an object of the invention to render thecharacteristic properties of the fine-bubble both layer formed lessdependent on the flow rate of the coffee extract jet and hence lessdependent on the pressure of the coffee extract being supplied to theinlet. In this manner, it is achieved that the apparatus can functionwell when coffeebeds with a varying thickness and grain size are used,and with apparatuses whose pressure of the coffee extract supplied tothe inlet, varies.

To that end, the apparatus according to the invention is characterizedin that in the buffer reservoir a liquid flow decelerating barrier,located at a distance from the upright sidewalls, is included.

The liquid flow decelerating barrier has as a result that the magnitudeof liquid flows and their associated turbulences in the buffer reservoirdecreases and is suppressed. It appears that even when the flow rate ofthe coffee extract jet increases substantially, the magnitude of theflow and its associated turbulences in the buffer reservoir increaseonly little. The result of this, in turn, is that the coffee extract isformed with a fine-bubble froth layer comparable to that with the lowerflow rate of the at least one coffee extract jet.

Preferably, the liquid flow decelerating barrier disposed between acentral part of the buffer reservoir and the upright sidewall so that aliquid flow from the central part in the direction of the uprightsidewalls and vice versa is limited.

In particular, the at least one coffee extract jet is directed towardsthe central part. The coffee extract jet, directed towards the centralpart will bring about the liquid flow from the central part in thedirection of the upright sidewalls of the buffer reservoir. Themagnitude of this liquid flow and the associated turbulence is limitedin that this liquid flow finds the liquid flow decelerating barrier inits path. Preferably, the buffer reservoir is provided with at least oneliquid discharge path for discharging coffee extract from the bufferreservoir to the at least one outlet, the at least one liquid dischargepath having its origin, viewed from the central part, outside the liquidflow decelerating barrier. Thus, it is achieved that all liquid which issupplied via the at least one coffee extract jet to the buffer reservoirhas to pass the liquid decelerating barrier in order to be able to leavethe buffer reservoir. The action of the liquid flow decelerating barrieris therefore very efficient.

In particular, the liquid flow decelerating barrier extends along afirst, closed curve, extending around the central part. It has appearedthat with such an embodiment, in a particularly efficient manner, theliquid flow and the associated turbulence within the buffer reservoir,is suppressed.

Furthermore, it is preferred that the liquid flow decelerating barrierextends along a second closed curve extending at a distance around thefirst curve. It has appeared that with such an embodiment, in anespecially efficient manner, the liquid flow and the associatedturbulence in the buffer reservoir are suppressed. Furthermore, inparticular, the liquid flow decelerating barrier is provided with anumber of obstacles, spaced apart and extending upward from the bottomof the buffer reservoir. These obstacles can, for instance, bepin-shaped. It is also possible that the liquid flow deceleratingbarrier be provided with a gauze wall extending from the bottom of thebuffer reservoir in a direction away from the bottom. Such a liquid flowdecelerating barrier also proves to function well.

It is further preferred that at least a part of the bottom is providedwith a roughened surface structure. It appears that, on the one hand,also with flow rates of the at least one liquid jet which are smallerthan those used in the know apparatus, the roughened surface bringsabout that a uniform fine-bubble froth layer is obtained. Therefore,this feature also has as a result that the range of the flaw rate of theat least one coffee extract jet, with which, in the known apparatus, acomparable fine-bubble froth layer is obtained, is increased in relationto the known apparatus. Additionally, the roughened surface structurehas as an advantage that a more uniform fine-bubble froth layer isobtained, i.e. that the variation in diameter of the bubbles formed issmaller than with the known apparatus if it were to have dimensionscomparable to the apparatus according to the invention.

According to the invention, therefore, it is achieved that, at equaldimensions of the apparatus according to the invention and the knownapparatus, with the apparatus according to the invention a more uniformfine-bubble froth layer is formed at a range of flow rates of the coffeeextract jet which is larger than the range of flow rates of the coffeeextract jet with the known apparatus. Here, the liquid flow deceleratingbarrier has as a particular result that the maximum of the range isincreased, while the roughened surface structure particularly results inthe minimum of the range being enlarged.

In particular, the apparatus is provided with two outlets, the liquidflow path extending from the inlet to the first outlet and to the secondoutlet. It appears that the liquid flow decelerating barrier has as anadditional advantage that with such an apparatus, to the two outlets,approximately the same amount of coffee extract with a fine bubble frothlayer is supplied. If each of the outlets is to fill one cup, both cupswill now be filled substantially equally. All this can be explained inthat the magnitude of the liquid flow and the associated turbulences inthe buffer reservoir has decreased as a result of the liquid flowdecelerating barrier. The liquid surface in the buffer reservoir iscalmer and will, therefore, be more evenly distributed over two liquiddischarge paths for discharging coffee extract from the buffer reservoirto the first and second outlet, respectively.

The invention will presently be further elucidated with reference to thedrawing. In the drawing:

FIG. 1 shows a transparent view of a first and second embodiment of anapparatus according to the invention;

FIG. 2 shows a cross section of a portion of the first embodiment of theapparatus according to FIG. 1;

FIG. 3 shows a cross section of a portion of the first and secondembodiment of the apparatus according to FIG. 1;

FIG. 4 shows a cross section of a portion of the first embodiment of theapparatus according to FIG. 1;

FIG. 5 shows a cross section similar to FIG. 2 of a portion of thesecond embodiment of the apparatus according to FIG. 1; and

FIG. 6 shows a cross section similar to FIG. 4 of a portion of thesecond embodiment of the apparatus according to FIG. 1.

In FIG. 1 reference numeral (1) designates an apparatus for preparing acoffee extract with a fine-bubble froth layer. The apparatus is providedwith at least one inlet (2), to which coffee extract can be supplied.Further, the apparatus comprises a first outlet (4.1) and a secondoutlet (4.2) for dispensing the coffee extract with the fine-bubblefroth layer. In use, under each outlet (4.1) and (4.2) a cup (5.1) and(5.2) can be placed to be filled with the coffee extract with thefine-bubble froth layer (café crème). It is also possible that a singlecup is placed under both outlets (4.1) and (4.2), so that only one cupis filled from both outlets.

The apparatus comprises at least one liquid flow path (6) which extendsfrom the at least one outlet (2) to the outlets (4.1) and (4.2). In use,the coffee extract flows from the at least one outlet along the liquidflow path (6) to the first and the second outlet (4.1) and (4.2). Theinlet (2) in this example is provided with a first and second spoutopening (8.1) and (8.2), which are each arranged for generating a liquidcoffee extract jet when coffee extract is supplied, in the example via aduct (10), to the inlet (2).

In the liquid flow path (6), a buffer reservoir (16) with a bottom (12)and an upright sidewall (18) is included, the arrangement being suchthat in use the coffee extract jets (14.1) and (14.2) generated by thetwo spout openings spout towards the bottom (12) when the coffee extractis supplied under pressure via the duct (10) to the inlet (2).

As a consequence of all this, in use, the coffee extract jets (14.1) and(14.2) spout into the buffer reservoir. Further, it holds in thisexample that at least a part of the bottom (12) is provided with aroughened surface structure. In this example, the entire bottom (12) isprovided with a roughened surface structure. However, the bottom mayalso be smooth.

The apparatus further comprises means (20), known per se, for generatingthe coffee extract and for supplying the coffee extract to the duct (10)at a pressure of, for instance, 0.3 to 3 atmosphere. The inlet with thespout openings brings about an increase of the flow velocity relative tothe flow velocity of the coffee extract in the duct (10). To that end,the surface area of each of the spout openings (8.1) and (8.2) equals,for instance, 0.05-0.5 mm².

The buffer reservoir (16) in this example is situated in a housing (22).The housing (22) comprises a bottom (24) with the outlets (4.1) and(4.2). Further, within the housing (22), outside the buffer reservoir(16), a partition (26) is arranged which divides a space in the middleof the housing (22), outside the buffer reservoir (16), into twomutually separate parts (28.1) and (28.2). The arrangement is such thatthe outlet (4.1) is in fluid communication with the first part (28.1) ofthe housing (22). Further, the outlet (4.2) is in fluid communicationwith the second part (28.2) of the housing (22). Further, in the bottom(12) of the buffer reservoir a first and a second drain opening (80.1)and (80.2) are provided. The first drain opening (30.1) forms a fluidcommunication between the inside of the buffer reservoir (16) and thefirst part (28.1) of the housing (22). Further, the second drain opening(30.2) provides a fluid communication between the insides of the bufferreservoir (16) and the second part (28.2) of the housing (22).

In the upright sidewall (18) of the buffer reservoir, a firstthrough-flow opening (32.1) is provided which extends from an upper sideof the sidewall in the direction of the bottom (12). The firstthrough-flow opening (32.1), however, does not extend as far as thebottom (12) and therefore constitutes an overflow from the bufferreservoir (16) to the first part (28.1) of the housing (22). Similarly,in the upright sidewall (18) of the buffer reservoir (16) a secondthrough-flow opening (32.2) is provided which constitutes an overflowfrom the buffer reservoir (16) to the second part (28.2) of the housing(22).

The apparatus (20), know per se, for preparing the coffee extract isprovided, in this example, with a container (40) which in use is filledwith water. In the container (40) a heating element (42) is arranged.The heating element (42) is arranged around a riser pipe (44) whichterminates in the bottom of a sachet holder (46). In use, the sachetholder (46) accommodates a sachet (47), made, for instance, of filteringpaper, which is filled with ground coffee (48). Placed on top of thesachet holder (46) is a lid (49) by which the reservoir (40), with thesachet holder (46) accommodated therein, is then closed offvapor-tightly. The duct (10) is in communication via the lid (49) withan inner space of the container (40).

Arranged in the buffer reservoir, further, is a liquid flow deceleratingbarrier (50) located at a distance from the upright sidewalls (18),indicated only schematically in FIG. 1. The function of the liquid flowdecelerating barrier is to reduce liquid flows and turbulences which inuse occur on a macroscale (i.e. for instance, a liquid flow from thecentral portion in the direction of the upright sidewall and vice versa)in the buffer reservoir. As can be properly seen in FIG. 2, the liquidflow decelerating barrier is included between a central portion (52) ofthe buffer reservoir, horizontally hatched in the drawing, and theupright sidewalls (18), so that a liquid flow from the central portionin the direction of the upright sidewalls and vice versa is limited. Thesmallest distance between the liquid flow decelerating barrier (50) andthe upright sidewall is indicated in FIG. 2 by the ‘D’. Similarly, thesmallest distance between the liquid flow decelerating barrier (50) andthe central portion (52) is indicated in FIG. 2 by ‘d’. In the example,the coffee extract jets (14.1) and (14.2) are directed towards thecentral portion (52). Accordingly, they will strike this central portion(52) depending on the height of the liquid level.

The drain openings (30.1) and (30.2) are situated between the uprightsidewall (18) and the liquid flow decelerating barrier (50). As aconsequence, the drain openings (30.1) and (30.2) as well as thethrough-flow openings (32.1) and (32.2) constitute liquid dischargepaths for discharging coffee extract from the buffer reservoir to theoutlets (4.1) and (4.2), these liquid discharge paths finding theirorigin outside, viewed from the central portion, the liquid flowdecelerating barrier (50).

In this example the liquid flow decelerating barrier (50) extends alonga first closed curve (54) extending around the central portion (52). Inthis example, the closed curve (54) is a circle. Further, the liquidflow decelerating barrier extends along a second closed curve (56),which extends around the first curve (54) at a distance ‘b’. In thisexample, the liquid flow decelerating barrier (50) is provided with anumber of spaced apart obstacles (58) extending upwards from the bottomof the buffer reservoir. In this example, the obstacles are ofpin-shaped design. Each obstacle can therefore consist of, for instance,a metal pin which reaches upwards from the bottom (12). The height ofthe pin can be equal, for instance, to the total height of the bufferreservoir or the height of the buffer reservoir adjacent thethrough-flow openings (32.1) and (32.2). However, the pips can also belower than the height of the buffer reservoir adjacent the through-flowopenings (32.1) and (32.2).

In this example, the pin-shaped obstacles (58) are disposed both on thefirst curve (54) and on the second curve (56), which is likewise ofcircular design.

The apparatus described up to this point works as follows. The reservoir(40) is filled with water. Next, with the aid of the heating element(42) the water is heated. As a result, the vapor pressure in thecontainer (40) will rise. The result is that the heated water in theriser pipe (44) is forced up towards the sachet holder (46). In thesachet holder (46), the water, hot by now, will be forced through thesachet (47). This yields coffee extract which is supplied under pressureto the duct (10). Under pressure, the coffee extract flows to the inlet(2). The coffee extract which is supplied under pressure to the inlet(2) squirts out via the spout openings (8.1) and (8.2), respectively.Thus, a first coffee extract jet (14.1) spouts towards the bottom (12)in the buffer reservoir (16). Similarly, a second coffee extract jet(14.2) spouts to the bottom (12) of the buffer reservoir (16). When thecoffee extract jets strike the bottom (12), then, as a result of theimpingement on the bottom (12), already some bubbles will be formed.Next, the buffer reservoir (16) will proceed to fill to some extent withthe coffee extract. In this example, the drain openings (30.1) and(30.2) have such dimensions that, in use, per unit time, more coffeeextract is supplied to the buffer reservoir (12) via the spout openings(8.1) and (8.2) than is discharged from the buffer reservoir via thedrain openings (30.1) and (30.2). Thus a layer of coffee extract isformed in the buffer reservoir. The apparatus is designed such that inuse in the buffer reservoir a layer of coffee extract is formed, whilethe at least one coffee extract jet spouts into the layer of coffeeextract that has been formed in the buffer reservoir. The height of theliquid level in the buffer reservoir can be, for instance, at least 5mm. Other values are also possible, however. The coffee extract jets(14.1) and (14.2) then squirt onto the liquid surface of the coffeeextract present in the buffer reservoir (16). As a result of a complexof factors, such as the coffee extract jets that squirt into the liquid,the coffee extract jets which albeit depending on the height of theliquid level in the buffer reservoir, spout against the bottom (12), andthe optionally roughened surface structure of the bottom which causeslocal turbulences on a microscale, a fine-bubble froth layer is formedon the coffee extract. Also, the roughened bottom, once a layer ofcoffee extract is present in the buffer reservoir, has the function inparticular of limiting or reducing the liquid flows in the bufferreservoir. When the liquid level has risen sufficiently, this will flowvia the through-flow opening (32.1) to the first part (28.1) of thehousing (22). Via the first part (28. 1) the coffee extract then flowsvia the outlet (4.1) into the cup (5.1). At the same time, coffeeextract with a fine-bubble froth layer will flow via the opening (32.2)in the upright sidewall (18) to the second part (28.2) of the housing(22). From the second part (28.2), the coffee extract with a fine-bubblefroth layer will flow via the outlet (4.2) to the cup (5.2).

It appears that by virtue of the fact that the bottom is provided with aroughened surface structure, given a coffee extract jet (14.1)comprising a flow rate of only 4 grams per second, already a predictablestable fine-bubble froth layer is formed on the coffee extract. The sameapplies to the coffee extract jet (14.2). In this example, the apparatus(23) is so dimensioned that each of the coffee extract jets comprises aflow of 6 grams per second. As a result of all this, even when the flowrates of the coffee extract jets will vary to some extent, and, forinstance, in the courses of time, or whatever reason, decrease, stillthe same kind of coffee extract with a fine-bubble froth layer isformed. The formation of coffee extract with a fine-bubble froth layeris therefore predictable. Moreover, it appears that by virtue of theroughened surface, the fine-bubble froth layer has a relativelyhomogeneous structure. This is to say that the range of diameters offormed bubbles is relatively small. Experts accordingly refer to afine-bubble froth layer of a uniform character.

When upon elapse of a predetermined time the apparatus (20) stopssupplying coffee extract to the inlet (2), the coffee extract jets(14.1) and (14.2) will be interrupted. The buffer reservoir can thendrain entirely via the drain openings (30.1) and (30.2). Thus, thebuffer reservoir drains towards the outlets (4.1) and (4.2).

Due to the fact that in use the openings (32.1) and (32.2) areoverflowed to an equal extent and the drain openings (30.1) and (30.2)are flowed through to an equal extent, the cups (5.1) and (5.2) will befilled with a presently substantially equal amount of coffee extract.

Preferably, it holds that the surface structure of the surface (12) hasa surface roughness corresponding to the surface roughness of sandpapercomprising particles having an average diameter of 50 to 2000 microns.In particular, it holds that the surface structure has a surfaceroughness corresponding to the surface roughness of sandpaper in therange of P12 to P300. Preferable, it holds that the surface structurehas a surface roughness corresponding to the surface roughness ofsandpaper in the range of P120 to P300.

Naturally, the roughness of the surface structure of the bottom (12) canalso be determined with other parameters. Thus, the surface structurecan also have a surface roughness Ra in a range of 50 to 2000 um.Preferably, however, Ra has a range of 50 to 200um.

The roughened surface structure can be provided in various ways. To beconsidered here are, for instance, a surface which has been subjected toa spark treatment. It is also possible that the surface (12) has beensand-blasted. In addition, it is possible that the surface has beenchemically etched. A combination of these techniques is also possible.

It is also possible that along the surface (12) a gauze (60) is arrangedfor obtaining the roughened surface structure. This is shown in FIG. 5.A gauze could be, for instance, a fabric of metal wires hang a pitchdistance and a diameter of the metal wires respectively corresponding tothe pitch and the diameter of wires of bandaid fabric. This metal fabriccan be provided on the bottom of the buffer reservoir by means of glue,for instance. It is also possible that on the gauze, in turn, a thinplastic covering layer or a coating has been provided. In effect,however, the bottom (12) will have a roughened surface structure.

The effect of the liquid flow decelerating barrier can be described asfollows. When the coffee extract jets (14.1) and (14.2) spout into thebuffer reservoir, they cause large currents in the buffer reservoirwhich are accompanied by large turbulences. This translates into avehemently whirling liquid surface in the buffer reservoir. It has beenfound that this vehemently whirling liquid surface has as a result thatthe possible range of the flow rate of each of the coffee extract jetsat which a uniform and predictable fine-bubble froth layer is formed, islimited. One can think of, for instance, a flow rate of 5 grams persecond to 5.5 grams per second, at which a uniform, even fine-bubblefroth layer is formed. If the flow rate for whatever reason increases ordecreases, a deviant or non fine-bubble froth layer will be formed.

The liquid flow decelerating barrier, however, has as a consequence thatthe magnitude of the liquid flows within the buffer reservoir (16) andthe attendant turbulences are reduced. It appears that the range of theflow rates of each of the coffee extract jets (14.1) and (14.2) at whichthe desired uniform fine-bubble froth layer is still obtained, isenlarged. The maximum of the range is raised to, for instance, 7 gramsper second. At the same time, the bottom (12) with its roughened surfacestructure has as a result that the minimum of the range is lowered to4.5 grams per second. Thus the range of the flow rates of the coffeeextract jets is enlarged considerably by virtue of the liquid flowdecelerating barrier. The roughened surface structure enhances thiseffect.

The liquid flaw decelerating barrier is used particularly effectively inthat all coffee extract must in principle pass the liquid flowdecelerating barrier (50), because on the one hand the coffee extractjets (14.1) and (14.2) are directed to the central portion (52) and onthe other hand the drain openings (30.1) and (30.2) as well as thethrough-flow openings (32.1) and (32.2) are located outside, viewed fromthe central portion (52), the liquid flow decelerating barrier. In otherwords, the coffee extract with the fine-bubble froth layer can leave thebuffer reservoir via liquid discharge paths whose origin, viewed fromthe central portion, is located outside the liquid flow deceleratingbarrier.

The liquid flow decelerating barrier (50) moreover has the advantagethat coffee extract with the fine-bubble froth layer will flow in anequal amount from the buffer reservoir to the first and second outlet(4.1) and (4.2), so that the cups (5.1) and (5.2) will presently befilled substantially equally. This is directly related to the fact thatby virtue of the liquid flow decelerating barrier, the liquid surface inthe buffer reservoir is relatively calm and will swirl little owing tothe suppressed turbulence and liquid flows in the buffer reservoir.

Referring to FIGS. 1, 5 and 6, presently a second possible embodiment ofthe apparatus 1 according to the invention will be discussed. Partscorresponding with the first embodiment are provided with the samereference numerals. In this apparatus, the bottom (12) of the liquidreservoir (16) is provided with the earlier mentioned gauze (60) forobtaining the surface with a roughened surface structure, as discussedhereinbefore. Further, however, the liquid flow decelerating barrier(50) is provided with an upright gauze wall (62) extending from thebottom (12) of the buffer reservoir (16) away from the bottom. The gauzewall (62) extends along the first curve (54). In this example, no gauzeextends along the second curve (56). The gauze wall (62) thereforeconstitutes a cylinder wall manufactured from gauze, through which thecoffee extract present in the buffer reservoir (16) can flow. The gauzewall consists, for instance, of wires of a diameter of 0.3 millimeter.These wires have been woven according to a linen binding with a pitch of1.5 millimeter. The function of the gauze wall is entirely comparablewith the functions of the pin-shaped projections (58) of the apparatusaccording to FIG. 2, and will therefore not be elucidated here.

The invention is not limited in any way to the exemplary embodimentsoutlined hereinbefore.

Thus, the bottom (12) of the buffer reservoir according to the FIGS. 1to 6, viewed from above, can be of slightly convex design. This promotesdrainage via the drainage opening (30.1) and (30.2). Also, the apparatusdoes not need to be provided with a bottom having a roughened surfacestructure. The bottom may therefore, for instance, be of smooth design.Also, only a part of the bottom 12 may be provided with the roughenedsurface structure. This part can coincide, for instance, with the area52 and/or lie within the curve 54. Also, in the apparatus according toFIGS. 1 to 6, the inlet (2) can be designed with only one spout opening(8.1), which is then located, for instance, in the middle of the inlet(2). Thus, only one coffee extract jet (14.1) is spouted into a bufferreservoir. The fine-bubble froth layer, however, is formed in anentirely analogous manner. Also, the cups (5.1) and (5.2) will be filledfrom the buffer reservoir, respectively, via the drain openings (28.1)and (28.2), the through-flow openings (30.1) and (30.2), and the outlets(4.1) and (4.2), as has been discussed hereinbefore.

In the apparatus according to FIGS. 1 to 6, the bottom (12) of thebuffer reservoir can coincide with the bottom (24) of the holder. Inthat case, however, the drain opening (30.1) and the through-flowopening (32.1) should be located above the outlet (4.1), and the drainopening (30.2) and the through-flow opening (32.2) should be locatedabove the outlet (4.2). The portion of the partition (26) which islocated in FIG. 1 between the bottom (12) and the bottom (24) is absentin that embodiment. Also, the through-flow openings (32.1) and (32.2)can be omitted. The drain openings (30.1) and (30.2) can then beenlarged to prevent the buffer reservoir overflowing while yet a layerof extract is formed in the buffer reservoir.

The normal of the bottom (12) of the buffer reservoir (16) can includean angle A with each of the coffee extract jets, which for instance, issmaller than 80 degrees, for instance equal to 45 degrees, andpreferably equal to zero degrees. Further, the sachet holder (46) andthe sachet (47) can be replaced with the assembly of European patent 0904 717. The opening in the bottom of the holder from the Europeanpatent 0 904 717 may then be further provided with a spout opening(nozzle) such as, for instance, the spout opening (18.1) described. Thebuffer reservoir may also be designed as described in Dutch patents1012847 and 1013270 while additionally the liquid flow deceleratingbarrier is arranged and optionally the roughened surface. In theexamples discussed here, the outlets each consist of an opening. This isnot requisite. An outlet can also consist of the through-flow opening(32.1) or (32.2), the drain opening (30.1) or (30.2) or another part.Such variants are all understood to fall within scope of the invention.

What is claimed is:
 1. An apparatus for preparing a coffee extract witha fine-bubble froth layer, provided with at least one inlet to whichcoffee extract is supplied, at least one outlet for dispensing thecoffee extract with the fine-bubble froth layer and at least one liquidflow path extending from the at least one inlet to the at least oneoutlet and along which, in use, the coffee extract flows from the atleast one inlet to the at least one outlet, while in the at least oneliquid flow path a buffer reservoir is included with an upright sidewalland a bottom, the at least one inlet being provided with at least onespout opening for generating at least one coffee extract jet which, inuse, squirts into the buffer reservoir when the coffee extract issupplied to the at least one inlet, characterized in that in the bufferreservoir a liquid flow decelerating barrier located at a distance fromthe upright sidewalls is included.
 2. An apparatus according to claim 1,characterized in that the liquid flow decelerating barrier is includedbetween a central part of the buffer reservoir and the uprightsidewalls, so that a liquid flow from the central part in the directionof the upright walls is limited.
 3. An apparatus according to claim 2,characterized in that the at least one coffee extract jet is directedtowards the central part.
 4. An apparatus according to claim 3,characterized in that the buffer reservoir is provided with at least oneliquid discharge path for discharging coffee extract from the bufferreservoir to the at least one outlet, the at least one liquid dischargepath having its origin, viewed from the central part, outside the liquidflow decelerating barrier.
 5. An apparatus according to claim 2, whereinthe liquid flow decelerating barrier extends along a first closed curve,extending around the central part.
 6. An Apparatus according to claim 5,characterized in that the liquid flow decelerating barrier furtherextends along a second closed curve, extending at a distance around thefirst curve.
 7. An apparatus according to claim 1, wherein the liquidflow decelerating barrier is provided with a number of obstacles,located at a distance from one another, extending upwards from thebottom of the buffer reservoir.
 8. An apparatus according to claim 7,characterized in that the obstacles are pin-shaped.
 9. An apparatusaccording to claim 1, wherein the liquid flow decelerating barrier isprovided with a gauze wall extending away from the bottom of the bufferreservoir.
 10. An apparatus according to claim 1, wherein the bottom, atleast partly, is provided with a roughened surface structure.
 11. Anapparatus according to claim 10, characterized in that the surfacestructure has a surface roughness corresponding to the surface roughnessof sandpaper comprising parts with an average diameter of 50-2000 μm.12. An apparatus according to claim 11, characterized in that thesurface structure has a surface roughness corresponding to the surfaceroughness of sandpaper in the range of P12 to P600.
 13. An apparatusaccording to claim 12, characterized in that the surface structure has asurface roughness corresponding to the surface roughness of sandpaper inthe range of P60 to P300.
 14. An apparatus according to claim 12,characterized in that the surface structure has a surface roughness-RAof 50-2000 μm.
 15. An apparatus according to claim 14, characterized inthat the surface structure has a surface roughness-RA of 50-200 μm. 16.An apparatus according to claim 10, wherein the bottom has beensubjected to a spark treatment.
 17. An apparatus according to claim 10,wherein the bottom has been sandblasted.
 18. An apparatus according toclaim 10, wherein the bottom has been chemically etched.
 19. Anapparatus according to claim 10, wherein on the bottom, a gauze isprovided far obtaining the roughened surface structure.
 20. An apparatusaccording to claim 1, wherein a normal of the bottom includes an angle Awith the coffee extract jet which is smaller than 80 degrees.
 21. Anapparatus according to claim 20, characterized in that the normal of thebottom includes an angle A with the coffee extract jet which isapproximately equal to 45 degrees.
 22. An apparatus according to claim20, characterized in that the normal of the surface includes an angle Awith the coffee extract jet which is approximately equal to zerodegrees.
 23. An apparatus according to claim 1, wherein the apparatus isfurther provided with means for preparing the coffee extract and forsupplying, under pressure, the coffee extract to the at least one inlet.